Merge tag 'fscache-fixes-20181130' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull fscache and cachefiles fixes from David Howells:
 "Misc fixes:

   - Fix an assertion failure at fs/cachefiles/xattr.c:138 caused by a
     race between a cache object lookup failing and someone attempting
     to reenable that object, thereby triggering an update of the
     object's attributes.

   - Fix an assertion failure at fs/fscache/operation.c:449 caused by a
     split atomic subtract and atomic read that allows a race to happen.

   - Fix a leak of backing pages when simultaneously reading the same
     page from the same object from two or more threads.

   - Fix a hang due to a race between a cache object being discarded and
     the corresponding cookie being reenabled.

  There are also some minor cleanups:

   - Cast an enum value to a different enum type to prevent clang from
     generating a warning. This shouldn't cause any sort of change in
     the emitted code.

   - Use ktime_get_real_seconds() instead of get_seconds(). This is just
     used to uniquify a filename for an object to be placed in the
     graveyard. Objects placed there are deleted by cachfilesd in
     userspace immediately thereafter.

   - Remove an initialised, but otherwise unused variable. This should
     have been entirely optimised away anyway"

* tag 'fscache-fixes-20181130' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  fscache, cachefiles: remove redundant variable 'cache'
  cachefiles: avoid deprecated get_seconds()
  cachefiles: Explicitly cast enumerated type in put_object
  fscache: fix race between enablement and dropping of object
  cachefiles: Fix page leak in cachefiles_read_backing_file while vmscan is active
  fscache: Fix race in fscache_op_complete() due to split atomic_sub & read
  cachefiles: Fix an assertion failure when trying to update a failed object

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c
index 40f7595aad10..8a577409d030 100644
--- a/fs/cachefiles/rdwr.c
+++ b/fs/cachefiles/rdwr.c
@@ -535,7 +535,10 @@ static int cachefiles_read_backing_file(struct cachefiles_object *object,
 					    netpage->index, cachefiles_gfp);
 		if (ret < 0) {
 			if (ret == -EEXIST) {
+				put_page(backpage);
+				backpage = NULL;
 				put_page(netpage);
+				netpage = NULL;
 				fscache_retrieval_complete(op, 1);
 				continue;
 			}
@@ -608,7 +611,10 @@ static int cachefiles_read_backing_file(struct cachefiles_object *object,
 					    netpage->index, cachefiles_gfp);
 		if (ret < 0) {
 			if (ret == -EEXIST) {
+				put_page(backpage);
+				backpage = NULL;
 				put_page(netpage);
+				netpage = NULL;
 				fscache_retrieval_complete(op, 1);
 				continue;
 			}
@@ -962,11 +968,8 @@ void cachefiles_uncache_page(struct fscache_object *_object, struct page *page)
 	__releases(&object->fscache.cookie->lock)
 {
 	struct cachefiles_object *object;
-	struct cachefiles_cache *cache;
 
 	object = container_of(_object, struct cachefiles_object, fscache);
-	cache = container_of(object->fscache.cache,
-			     struct cachefiles_cache, cache);
 
 	_enter("%p,{%lu}", object, page->index);